Homoallyl alcohols can be prepared, for example, by a reaction known as the Prins reaction, which generally refers to the electrophilic addition of an aldehyde or ketone onto an alkene followed by addition of a nucleophile onto the resulting intermediate. An ene reaction is also possible for this purpose; this is generally known as a pericyclic reaction in which an alkene bearing a hydrogen in the allylic position is reacted with a compound having a multiple bond. It proceeds with increased difficulty, the higher the degree of substitution in the allylic position which bears the proton to be transferred.
The prior art is summarized below:
JACS 1955, 77, 4666-8 describes the uncatalyzed thermal addition of paraformaldehyde onto dialkyl-substituted terminal olefins under superatmospheric pressure and elevated temperature. Specifically, the conversion of isobutene into 3-methyl-3-buten-1-ol is described and the influence of various reaction conditions is indicated.
JACS 1982, 104, 555-63 discloses the catalyzed Prins reaction of aldehydes. A general problem associated with ene reactions of aldehydes (paraformaldehyde) catalyzed by a Lewis acid is said to be the alcohol-Lewis acid complex formed, which is sensitive to solvolysis. In addition, it is a strong protic acid which can protonate the double bond.
U.S. Pat. No. 4,511,751 describes the reaction of isobutene and/or tertiary butanol with formaldehyde in an acidic aqueous solution. Since the alcohol function is eliminated, the reaction product (at temperatures >150° C.) is not the unsaturated alcohol isoprenol but isoprene.
Chem. Commun. 2001, 992-3 teaches that the direct immobilization of catalysts on inorganic support materials can be disadvantageous because decreases in activity can occur because of leaching. As an alternative, it is indicated that the metal catalyst (SnCl4) can be anchored via tetraalkylammonium chloride on the support (MCM-41) and the activity could be retained in this way. The cation is covalently bound to the surface of the support via a siloxane function; this chemical fixing makes a plurality of chemical reactions necessary. Reactions of isobutene with paraformaldehyde in a nonaqueous medium have confirmed the hypothesis.
According to Angew. Chem. Int. Ed. 2005, 44, 815-9, SILP (supported ionic liquid phase) catalyst systems can be used for olefin hydroformylation (Rh-catalyzed), hydrogenation (Rh-catalyzed), Heck reactions (Pd-catalyzed) and hydroamination (Rh-, Pd- and Zn-catalyzed). The INV0070434 MST/Ya Apr. 8, 2011 0 FIG./0 Seq transition metal complexes are here dissolved in a thin film of ionic liquid which is held on a porous solid having a large surface area by physisorption or else by covalent anchoring.